We present an epidemiologic characterization of deaths from motor vehicle immersions, based on 77 deaths in 63 motor vehicle immersions in Sacramento County, CA, during 1974-85. All persons were autopsied; all but one of the deaths were due to drowning. Average annual mortality rates per million person years were 12 for males, four for females, 30 for Hispanics, six for White non-Hispanics, Blacks and Asians. Seventy-one percent of drivers and 60 percent of passengers had a blood alcohol concentration greater than or equal to 22 mmol/L. Most cases (57 percent) had an Injury Severity Score of 1 (minor injury) or 0 (no injury). Alcohol use was associated with higher Injury Severity Scores. Road curvature of 20 degrees or greater was far more common at crash sites than at matched control sites one mile away (OR = 6.57, 95% CI = 2.93, 14.71). Guard rail placement along highly curved sections of roadway may be an effective preventive measure.